Tonkin was recently with the Rochester Red Wings, the Triple-A affiliate of the Twins. With the Twins this year, he's posted a 5.63 ERA and 1.50 WHIP over eight innings of relief this season.

Twins return Michael Tonkin to Triple-A after Wednesday twinbill

by Igor Mello | CBSSports.com

(6/4/15) The Twins optioned right-hander Michael Tonkin to Triple-A Rochester on Thursday, according to the team's official website. Tonkin served as Minnesota's 26th man in Wednesday's doubleheader in Boston. He held a 5.63 ERA and 1.50 WHIP over eight innings of relief this season.

RP Casey Fien returns to Twins, RP Michael Tonkin demoted

by Marty Gitlin | CBSSports.com

(5/29/15) The Twins have reinstated Casey Fien from the disabled list and optioned fellow right-handed reliever Michael Tonkin to Triple-A Rochester, per MLB.com.

Fien, who has recovered from a shoulder injury, lost his setup role during his absence. He returns with a 1-2 record and 4.35 ERA.

Twins place Casey Fien on DL, promote Michael Tonkin

by Marty Gitlin | CBSSports.com

(4/30/15) The hope of the Twins that key reliever Casey Fien could avoid a stint on the disabled list has been dashed, FoxSportsNorth is reporting. The right-hander has been placed on the 15-day DL with a shoulder injury sustained during his ninth-inning appearance Wednesday against Detroit.

Fien has had two poor performances since his three scoreless, hitless appearances to start the season. His ERA catapulted from 1.93 to 4.35 when he allowed three runs on five hits to the Tigers.

His replacement is fellow righty Michael Tonkin, who has been promoted from Triple-A Rochester. Tonkin pitched in 25 games for Minnesota a year ago and had yielded just two earned runs with 10 strikeouts in 7 1/3 innings at the Triple-A level in 2015.